Figure 1: Human vascular smooth muscle cells rate soften at both physiological and supraphysiological strain rates.

a, Micropatterned vascular smooth muscle cell on deformable membrane. b, Microscope-mounted high-speed CμBS device for performing traction force microscopy on deformed cells. c, Cells are stretched at strain rates of 0.001 s⁻¹ (slow, black), 0.005 s⁻¹ (medium, purple), 0.05 s⁻¹ (fast, red), or 10 s⁻¹ (trauma, yellow) and held at 0.15 strain. 5 minutes after initiation of stretch, cells are returned to 0 strain at the same rate and held static. This cycle is repeated 3 times. Inset: First 0.5 s of deformation to visualize trauma strain rate. d, Brightfield image (top), underlying fluorescent bead layer image (2^nd from top), and traction stress maps (bottom 5) at 5 timepoints for a representative cell stretched at the slow strain rate. Scale bar, 20 μm. e, Average normalized axial PK1 stress ($P_x$) vs time for cells stretched according to the protocol in c. Stress decreases and cells soften with increasing strain rate, and stress drops below basal stress in the trauma rate. n = 16, 14, 20, 15 cells, respectively. f, Normalized peak (immediately after completion of stretch) and decay (5 minutes after initiation of stretch) stress for first deformation cycle. Solid bars: mean, open circles: individual measurement. *p < 0.05, **p < 0.01, ***p < 0.001. Error bars represent standard error of the mean (s.e.m.).